David Cameron and Lord Forsyth reject whispering campaign against performance
of Better Together and its leader, Alistair Darling

David Cameron and a senior Tory peer have praised Alistair Darling’s leadership of the campaign against Scottish independence in a fierce rebuttal of a whispering campaign by disgruntled Conservatives.

The Prime Minister and Lord Forsyth of Drumlean, a former Scottish Secretary, also rejected criticism that the pro-UK Better Together campaign risked losing September’s referendum by being too negative.

Mr Cameron said the campaign’s arguments about the impact of Scottish separation on the currency, Europe, defence jobs and financial services were “strong and very solid”.

Lord Forsyth also rejected criticism of Better Together’s tone, stating that it was right to highlight the implications of a proposal that would have a negative impact on Scotland and England.

Their rebuttal emerged following the publication of comments attributed to senior Tories attacking Mr Darling for being “comatose” and even proposing he be replaced with Jeremy Hunt, the English Health Secretary.

Lynton Crosby, the Prime Minister’s election guru, has issued an emphatic denial he is behind the whispering campaign amid rumours that polls giving the unionists a commanding lead are wrong and Alex Salmond’s separatists are likely to triumph.

Downing Street sources rejected the claims about Mr Crosby as “second and third-hand tittle-tattle” and claimed the real culprit was someone without any close involvement in the fight against independence.

They pointed out that Mr Salmond’s publication of his keynote White Paper last month had failed to produce any ‘bounce’ in support for independence despite his claim it is the prospectus on which voters will be casting their ballots.

In an interview with the Spectator, the full details of which were published today, Mr Cameron said he thought that Mr Darling was performing “very well”.

“We cannot in any way let this argument go the wrong way. We’ve got to fight every day. It’s one of the biggest issues of next year, if not the biggest,” the Prime Minister said.

“I desperately want it to go the right way and I think the arguments that Better Together and the UK Government will be making are very strong and very solid.

“The arguments about defence jobs, the arguments about currency, the arguments about Europe, the arguments about financial services, the arguments about future fiscal trends – I think they’re really impressive, substantial pieces of work.”

He added: “Alistair is playing a key part of that. So I think the argument is going well but we need to keep up the pressure.”

The Sunday Times reported Lord Forsyth’s concerns that the UK Government is complacent about the result, but he told the Telegraph that Mr Darling, the former Chancellor, was doing a “great job” and criticism of Better Together is “unfounded”

“They’ve set out the reality – the consequences of breaking up the United Kingdom would be very negative indeed for Scotland, England, Wales and Northern Ireland,” he said.

“If somebody wants to break up a successful marriage, which is what Alex Salmond wants to do, it’s for them to make the case, not the people who are happily married.”

But a spokesman for Mr Salmond reiterated his challenge for televised debate on independence, adding: “It is time David Cameron stopped hiding behind 'comatose Darling' and debated with the First Minister face to face. Senior figures on the No campaign appear to be pulling the panic cord.”